The present invention relates generally to speed changers of the kind comprising two pulleys, driving and driven respectively, each of which comprises a hub and two annular flanges facing each other around the said hub to receive a belt, one of the flanges being axially movable relative to the hub and being subjected to annular elastic means which urge it continuously towards the other flange, which is fixed, these elastic means bearing against the movable flange and an integral bearing piece of the hub.
For controlling the configuration of the assembly and thus the transmission ratio, the movable flange of at least one of the pulleys is subject to the action of elastic return means which urge it continuously towards the fixed flange, and which comprise an annular piece with a variably conical shape known as a diaphragm, which through a peripheral part forming a Belleville washer, bears axially indirectly on the movable flange and which, through a central part divided into radial fingers, bears indirectly on the axially permanently fixed bearing piece of the hub.
Such a speed changer is described in U.S. Pat. No. 4,559,026.
In this document a bridging element is permanently fixed to the diaphragm by being glued or fastened thereto and is permanently fixed to the movable flange either directly by being glued or fastened to the flange, or by means of a connecting piece glued or fastened to the bridging element and fixed to the movable flange by clamping with lugs, by clipping, by riveting or by soldering.
The bridging element interposed in this way between the diaphragm and the movable flange and its method of assembly present disadvantages.
Among these disadvantages must be mentioned an increased axial space requirement resulting from the bridging element and the operations of fastening or glueing, with or without a bridging element, which are lengthy and delicate and consequently have a relatively high cost. In addition, if the attachment of the bridging element to the movable flange is effected by lugs, clips or rivets it is necessary also to provide sealing joints in the case of a speed changer controlled by a pressurised fluid.
The invention reduces these disadvantages whilst providing reliable connection between the diaphragm and the movable flange to ensure a good transmission of torque.